ENH: df.to_csv() and pd.read_csv() defaults do not give back original data

[edmundsj]

Is your feature request related to a problem?

I expect when loading and saving CSV data that whatever defaults used for loading and saving can be used mindlessly if my data is simple enough. For example, in the below example, I would expect that new_df is equal to df:

df = pd.DataFrame({'time (ms)': [1, 2, 3, 4]})
df.to_csv('test.csv')
new_df = pd.read_csv('test.csv')

However, this is not so. The index is saved as the first column by default, but is not read as the first column by default when loading data with read_csv().

Describe the solution you'd like

I should not have to pass in additional arguments to get the simplest use case to work for loading and saving data. I suggest either not saving the index by default when converting to CSV (this seems less desirable), or setting the index_col=0 by default when loading a CSV file.

API breaking implications

index_col would be set by default

Describe alternatives you've considered

Manually avoiding saving the index, and manually adding the index_col=0 keyword argument when loading CSV data. Both have caused me endless frustration.

[jreback]

search for from_cav in the issue tracker

this was changed a long time ago and lots of discussion on why this is

[edmundsj]

from_cav yields only this result. Can you link to the specific discussion?

[jreback]

#4595

https://github.com/pandas-dev/pandas/issues?q=from_csv yields 49 results so other commentary